Engine starter gearing



Feb. 29, 1944. E. E. HOOD ENGINE STARTER GEARING Filed May 22, 1942 2 Sheets-Sheet l 29, 1944- i E. E. HOOD 2,342,632

ENGINE STARTER GEARING Filed May 22, 1942 I 2 Sheets-Sheet 2 INVENTOR.

Patented Feb. 29, 1944 uNrrso STATES PATENT OFFICE ENGINE STABTERGEARING E. Elliott Hood, Elmira, N. Y., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delawarq Application May 22, 1942, Serial No. 444,015 7 Claims.

The present invention relates to engine starter earing and more particularly to an automatically operated detent for ensuring traversal of a starter drive pinion into mesh with a member of an engine to be started.

Various forms of detent have heretofore been used in connectiorrwlflr engine starter gearing of the automatically engaging type, to ensure the desired traversal of the pinion under adverse conditions. It is an object of the present in vention to provide a novel detent arrangement which is efficlent and reliable in operation while being free from interference with the cranking function of the drive.

It is another object to provide such a device in which the detent is arranged to be actuated simultaneously with the energization of the starting motor, and to be released when the drive is fully engaged.

It is another object to provide such a device in which the release of the detent is consequential to the assumption of the cranking load by the drive.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a semi-diagrammatic illustration of a starting system showing a preferred embodiment of the invention;

Fig. 2 is a diagrammatic representation of a variation of the electrical system shown in Fig. 1; and

Fig. 3 is .a view similar to Fig. l of a further embodiment of the invention.

In Fig. l of the drawings there is illustrated an engine starting system, including a battery grounded at 2 and connected through a starting switch 3 and cable 4 to a starting motor SM which is grounded at 5 to complete the cranking circuit.

The motor is arranged to operate a power shaft 6 which drives a screw shaft 1 through gears 8 and 3, and a pinion II is threaded on the screw shaft for movement into and out of engagement with a gear |2 of the engine to be started.

According to the present invention a detent indicated generally by numeral I3 is arranged to oppose initial rotation of the pinion in order to ensure its traversal along the screw shaft into engagement with the'engine gear. As here shown detent |3 comprises a. magnetic plunger H and an electromagnet IS, the plunger being normally maintained free of the pinion by a retracting spring M. A circuit is provided for actuating the detent simultaneously with the application of current to the starting motor: As here shown this circuit comprises a relay l1 having an armature II connected by a lead IS with the cranking circuit cable 4 and having a contact 2| normally in. engagement with a stationary contact 22 which is connected by a lead 23 to the electromagnet I5, said electromagnet being grounded at 24 to complete the detent-actuating circuit.

Means for causing the release of the detent responsive to the assumption of the cranking load by the motor i provided comprising a control relay 25 having an armature 26 connected by a lead 21 with the detent circuit lead l9 and having a contact 23 normally in engagement with a fixed contact 29. A coil 3| connected by a lead 32 to the control relay lead 21 and grounded at 33 is arranged to attract the armature 26 and open contacts 28, 23 when the full battery voltage is applied to said coil. The relay 25 is so designed however that coil 3| will release the armature 26 and permit contacts 28, 29 to close when the voltage in the cranking circuit is reduced by the heavy current drain caused by the starting motor when it first assumes the cranking load.

Contact 29 of control relay 25 is connected by a lead 34 to coil 35 and fixed contact 36 of relay ll, coil 35 being grounded at 31 to complete the relay circuit. Coil 35 is constructed in any conventional manner as a comparatively slowacting electromagnet which when energized attracts armature l3 to open contacts 2|, 22 and close contacts 2|, 36.

In the operation of this embodiment of the invention, starting with the parts in the positions illustrated, closure of the starting switch 3 by the operator completes the crankin circuit through the starting motor and causes the screw shaft 1 to be rotated thereby. Closure of the starting switch 3 also completes the detent-actuating circuit through lead l3. contacts 2|, 22 and lead 23 to the electromagnet |5 thus causing the plunger II to engage the teeth of the pinion H and resist rotation thereof to ensure its traversal into engagement with the engine gear I2.

Closure of starting switch 3 also completes the circuits through coil 3| of relay 25, and coil 35 of relay I1. Coil 3|, however, is effective to open contacts 28, 23 before coil 35 opens contacts 2|, 22, due to the slow-acting character of coil 35, so that contacts 2|, 22 remain closed.

When the pinion reaches the end of its travel on the screw shaft 1, said shaft is constrained to rotate the pinion and assume the cranking load of the engine. The consequent momentary stalling of the starting motor SM causes a very heavy current drain through the cranking circuit which substantially reduces the voltage aplied tov the coil 8| of relay 25. This reduction in voltage is arranged to permit closure or contacts 28, 29, and the consequent energization of coil 35-.which attracts the armature I8 of relay l1, opening contacts 2|, 22 and closing contacts 2|, 36. The opening of contacts 2|, 22 breaks the detent circuit whereby the plunger I4 is released from the pinion II' by the retracting spring l6. Closure of contacts 2|, 36 completes a holding circuit from lead |9 through coil 35 whereby the armature I8 is held down as long as the starting switch 3 remains closed, irrespective of the opening of contacts 28, 29 of relay 25. When the cranking operation is completed and the operator opens the starting switch 3, the parts return totheir idle positions as illustrated.

In Fig. 2 of the drawings there is illustrated an embodiment of the invention incorporating a control relay which is dependent for its operation on variations in current flow in the cranking circuit. As there shown, a control relay 25' has a coil 3| connected in'series in the cranking circuit, and an armature 26' carrying a contact 28' adapted to cooperate with a fixed contact 29' but normally held out of engagement therewith by a spring 30. The remaining parts are the same as shown in Fig. 1 and are similarly numbered.

In operation, closure of starting switch 3 energizes the starting motor, and at the same time actuates the-detent l3 to oppose rotation of the pinion. When the pinion is fully meshed with the engine gear and the motor assumes the cranking load, the heavy current through the coil 3| causes the contact 28., 29' to close, thereby energizing coil 35 of relay I1. Contact 2| is thus caused to leave contact 22 and engage contact 36, whereby the detent control circuit is opened and detent I3 is released.

at 18 is provided for opposing rotation of the pinion 68 to ensure its meshing operation. This detent comprises a plunger 19 normally retracted from the pinion by a spring 8| but adapted to be moved into engagement with the teeth of the pinion by means of a coil 82. An actuating circuit for the detent 18 is provided comprising a lead 83 connecting the lead 61 to a coil 84 in the control relay 11. The opposite end oi coil 84 is connected to the armature 16, and by a lead 85 to the detent coil 82 which is grounded at 86 to complete the actuating circuit. Armature 18 is provided with a contact 81 adapted to engage a fixed contact 88 which is grounded at 89, said contacts being normally held out of engagement by suitable means such as a spring 9|.

Means are provided for causing release of the detent 18 when the starting motor assumes the cranking load, which means comprises a coil 9| in the relay 11, on end oi which is connected to the lead 83 and the other end is connected by a lead 92to the starting motor cable 56 so that the coil 9| is, in eiiect, arranged in parallel with the resistor 55. Coil 9| is thus energized by the voltage drop acros the resistor 55 and when so energized causes closure of contacts 81, 88.

In the operation of this embodiment Of the invention closure of the starting switch 53 causes energization of the starting motor throughthe resistor 55 whereby the screw shaft 59 is rotated. At the same time the coil 82 of the detent 18 is energized by current traversing leads 61, 83, coil of relay 65 and lead 15, but the coil 86 and 18 In Fig. 3 of the drawings there is illustrated a starting system which provides for energization of the starting motor in two stages. During the.

a battery 5| grounded at 52 and connected by a starting switch 53 to a cable 54 leading to a resister 55 of suitable value for reducing the battery voltage to decrease the shock of engagement of the gear. A cable 56 connects the resistor 55 to the starting motor SM which is grounded at 51 to complete the starting circuit. Motor SM is arranged to actuate a power shaft 58 which drives a screw shaft 59 through gearings 6| and 62. A pinion 63 is threaded on the screw shaft 59 for movement into and out of engagement with an engine gear 66.

An electromagnetic switch 65 is arranged to short circuit the resistor 55 after the pinion 63 is fully engaged with the engine gear 64. Switch 65 comprises a contact 66 connected by a lead 61 to the starting circuit cable 54, a contact 68 connected by a lead '69 to the starting motor cable 56, and a bridging contact 1| mounted on a plunger 12 arranged to be actuated by a coil 13. One end of coil 13 is connected by a lead 14 to the lead 81, and the other end is connected by a lead 15 to the armature 16 of a control relay indicated generally by numeral 11.

An electromagnetic detent indicated generally are so designed that the current traversing these coils when they are thus in series with the detent coil 82 is insumcient to cause coil 84 to close contacts 81. ,88, or "coil 13 to cause closure of contacts 66, 1|, 68.

When the pinion 63 is completely meshed with the engine gear and its traversal arrested by the stop 93, the starting motor is stalled by the resistance oi the engine to rotation. The voltage drop across the resistor 55 thus increases to a maximum which is sufflcient to energize coil 9| of relay 11 to cause closure of contacts 81, 88. Th detent 18 is thereby released by the deenergization of coil 82, and at the same time the coil 84 is fully energized so as to hold contacts 81, 88 closed, and coil 13 is also fully energized so as to cause closure of magnetic switch 65, thus bridging the resistor'55 and causing energization of'the starting motor by the full battery voltage.

Cranking of the engine thereupon takes place. the parts being maintained in the stated positions as long as the starting switch '53 is held closed.

, When the engine starts and the operator opens sisting rotation of the pinion, electromagnetic means for actuating the detent energized simultaneously with application of current to the starting motor, and means responsive to the assumption of the cranking load by the motor for causing release of the detent.

2. In an engine starting system a starting motor, a power shaft driven thereby, a pinion threaded on the power shalt, a detent for resisting rotation of the pinion, electromagnetic means for actuating the detent energized simultaneously with application of current to the starting motor, means including a relay for deenergizing said electrpmagnetio means, and means responsive to completion or the driving connection from the motor to the engine for actuating said relay.

3. In an engine strrting system a starting motor, a power shaft 'iriven thereby, a pinion threaded on the power sirait, a detent for resisting rotation 01' the pinion, electromagnetic means for actuating the detent energized simultaneously with application of current to the starting motor, means including a relay having a pair aasass:

of contacts, closure 0! which eilects de-energiza- 25 the voltage drop across the resistor when thestarting motor stalls ior de-energising said electromagnetic means and for shorting out the resistor, and means for maintaining the electromagnetic means de-energised thereafter as long as the starting switch remains closed.

5. In an engine starting system a starting circuit including a starting switch, a resistor and a motor in series therewith, a switch for bridging the resistor, a power shalt driven by the motor, a pinion having a threaded connection with the power shai't, a magnetically operable detent i'or resisting rotation 01 the pinion to ensure its traversal, means energized by closure oi starting switch for actuating the detent, and means ineluding a relay having a coil in shunt with the resistor and energized by the voltage drop across the resistor whenthe starting motor stalls to effect release of the detent and to close the bridging switch.

E. EILIO'II HOOD. 

